Disconnector is a mechanical switch for isolating electrical devices from a power line, which is typically used in high voltage environment to form a visible disconnecting point to ensure a reliable isolation of electrical devices from a power line, such that the electrical devices can be operated or maintained safely without load. Usually, at least one earthing switch is used together with the disconnector to connect the isolated electrical devices to the ground such that a capacitive current or an inductive current remained on the isolated electrical devices can be eliminated and the isolated electrical devices can be operated or maintained more safely.
It is a basic requirement that a disconnector and the associated earthing switches cannot be in closed state at the same time, otherwise it would result in an accident leading a large current into ground. Therefore, it is necessary to provide an interlock mechanism between a disconnector and the associated earthing switches to avoid the close of the disconnector and the associated earthing switches at the same time due to wrong operation by an operator error or a failure in actuating devices for the disconnector and the associated earthing switches.
The existing mechanical interlocks between a disconnector (i.e. DS) and the associated earthing switches (i.e. ES) are mostly provided on the mechanism side and on vertical transmitting rods. These interlocks need welding parts or splined shaft to mount the interlocks on the vertical transmitting rods. These structures are not only very complicated and expensive, but also quite difficult for installation and maintenance. For the existing interlocks between a disconnector and associated earthing switches located at long distance from the disconnector, the interlocks are more complicated and less reliable, and are also quite difficult for installation and maintenance.
Therefore, it requires to provide an interlock mechanism between a disconnector and associated earthing switches, which is more simple in structure and more reliable, and is easy for installation and maintenance.